Flexible cover window and display device including the same

Abstract

A flexible cover window according to one embodiment of the technical concept of the present disclosure comprises a glass substrate that is divided into a deformation region that is deformed along a deformation axis extended in one direction when an external force is applied, and a non-deformation region connected to the deformation region, and includes a recess pattern formed in the deformation region, wherein the recess pattern includes a plurality of recesses etched to a predetermined depth from one surface of the glass substrate, and the plurality of recesses include a first recess formed in a region including the deformation axis; and at least one second recess formed on at least one side of the first recess, wherein the depth of the first recess is formed deeper than the depth of the second recess.

Description

Technology Field

[0001] The technical concept of the present disclosure relates to a flexible cover window capable of smoothly undergoing deformation, such as folding or bending, in a predetermined area, and a display device including the same. Background Technology

[0003] Flexible displays have been continuously researched as a factor capable of diversifying the form factors of various portable terminals and electronic devices, and recently, they are being commercialized by being incorporated into smartphones and TVs.

[0004] Research on such flexible displays is being conducted in forms such as foldable, rollable, slideable, and stretchable. To implement a flexible display, not only the display panel but also the cover window protecting the display panel must be formed to be flexible.

[0005] Conventionally, polyimide films or single-thickness ultra-thin glass (UTG) have been used as cover windows for flexible displays. However, polyimide films have relatively low hardness, leading to problems such as permanent deformation or wrinkling. Additionally, UTG has low durability against external impacts, resulting in damage to the display or device.

[0006] Accordingly, research is currently being conducted on a method to improve durability and flexibility by varying the thickness of UTG in different regions. The problem to be solved

[0008] The problem that the present invention aims to solve is to provide a flexible cover window that can secure deformation characteristics and strength characteristics of a flexible cover window implemented with glass. means of solving the problem

[0010] To achieve the above objectives, a flexible cover window according to one aspect of the technical concept of the present disclosure comprises a glass substrate that is divided into a deformation region that is deformed along a deformation axis extended in one direction when an external force is applied, and a non-deformation region connected to the deformation region, and includes a recess pattern formed in the deformation region, wherein the recess pattern includes a plurality of recesses etched to a predetermined depth from one surface of the glass substrate, and the plurality of recesses include a first recess formed in a region including the deformation axis; and at least one second recess formed on at least one side of the first recess, and the depth of the first recess is formed deeper than the depth of the second recess.

[0011] According to one embodiment, each of the plurality of recesses forms a curved surface with a cross-section that is curved in a direction from one surface to another surface, and may be connected by partially overlapping with an adjacent recess.

[0012] According to one embodiment, the recess pattern may have a shape symmetrical about the deformation axis.

[0013] According to one embodiment, the width of the first recess may be formed wider than the width of the second recess.

[0014] According to one embodiment, the plurality of recesses further include at least one third recess formed on the side opposite to the first recess among both sides of each of the at least one second recess, and the width and depth of the at least one third recess may be formed to be smaller than or equal to the width and depth of the at least one second recess.

[0015] According to one embodiment, the flexible cover window further includes a cushioning member filled in an area corresponding to the recess pattern, and the cushioning member may include at least one of OCA (optical clear adhesive) and PSA (pressure sensitive adhesive).

[0016] According to one embodiment, the sum of the thicknesses of the glass substrate in the area filled with the buffer member and the buffer member may be the same as the thickness of the glass substrate in the area not filled with the buffer member.

[0017] According to one embodiment, the flexible cover window further comprises a coating layer formed on at least one surface of the glass substrate, and the coating layer may comprise at least one of an AF (anti-fouling) film, an AR (anti-reflective) film, and a scratch-resistant film.

[0018] According to one embodiment, the recess pattern may include a first recess pattern formed on one side of a deformation region of the glass substrate; and a second recess pattern formed on the other side of the deformation region of the glass substrate.

[0019] According to one embodiment, the sum of the maximum depth of the first recess pattern and the maximum depth of the second recess pattern may be greater than the thickness of the glass substrate.

[0020] A display device according to one embodiment of the technical concept of the present disclosure may include the flexible cover window described above. Effects of the invention

[0022] According to the technical concept of the present disclosure, by reducing the glass thickness in the area where deformation of the flexible cover window occurs, it is possible to provide a flexible cover window with excellent deformation characteristics while maintaining the inherent texture of the glass.

[0023] In addition, since a predetermined thickness can be maintained in areas where deformation of the flexible cover window does not occur, the problem of reduced strength due to the reduction in the overall thickness of the glass can be prevented.

[0024] In addition, by filling the recess pattern area of ​​the glass with a cushioning material, sufficient flexibility of the glass can be provided, and by keeping the display surface of the flexible cover window flat, degradation of image quality or distortion can be prevented.

[0025] The effects obtainable through a flexible cover window according to the technical concept of the present disclosure are not limited to the effects mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present invention belongs from the description below. Brief explanation of the drawing

[0027] A brief description of each drawing is provided to help to better understand the drawings cited in the present disclosure. FIG. 1 is a schematic perspective view of a display device including a flexible cover window according to an embodiment of the present disclosure. FIG. 2 is a perspective view of a display device folded based on a folding axis according to an embodiment of the present disclosure. FIGS. 3 to 5 show an example of a cross-sectional view of a flexible cover window cut along A-A' shown in FIG. 1. FIG. 6 shows another embodiment of a cross-sectional view of a flexible cover window cut along A-A' shown in FIG. 1. FIGS. 7 to 8 show an example of a manufacturing process for a flexible cover window according to the embodiments of FIGS. 3 to 5. FIG. 9 is a cross-sectional view of a flexible cover window according to one embodiment of the present disclosure. FIG. 10 is a cross-sectional view of a flexible cover window according to one embodiment of the present disclosure. Specific details for implementing the invention

[0028] Exemplary embodiments according to the technical concept of the present disclosure are provided to more fully explain the technical concept of the present disclosure to those skilled in the art, and the following embodiments may be modified in various different forms, and the scope of the technical concept of the present disclosure is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more faithful and complete and to fully convey the technical concept of the present invention to those skilled in the art.

[0029] In this disclosure, terms such as "first," "second," etc. are used to describe various members, regions, layers, parts, and / or components; however, it is obvious that these members, parts, regions, layers, parts, and / or components should not be limited by these terms. These terms do not imply a specific order, hierarchy, or superiority, and are used solely to distinguish one member, region, part, or component from another. Accordingly, the first member, region, part, or component described below may refer to the second member, region, part, or component without departing from the teachings of the technical concept of this disclosure. For example, without departing from the scope of rights of this disclosure, the first component may be named the second component, and similarly, the second component may be named the first component.

[0030] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art to which the concept of this disclosure belongs. Furthermore, commonly used terms, such as those defined in advance, should be interpreted as having a meaning consistent with what they mean in the context of the relevant technology, and should not be interpreted in an overly formal sense unless explicitly defined herein.

[0031] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or in the reverse order of the description.

[0032] In the attached drawings, variations of the depicted shapes may be expected, for example, depending on manufacturing technology and / or tolerances. Accordingly, embodiments based on the technical concept of the present disclosure should not be interpreted as being limited to specific shapes of the areas depicted in the present disclosure, but should include, for example, changes in shape resulting from the manufacturing process. Identical reference numerals are used for identical components in the drawings, and redundant descriptions thereof are omitted.

[0033] The term 'and / or' as used herein includes each of the mentioned members and all combinations of one or more.

[0034] Hereinafter, embodiments according to the technical concept of the present disclosure will be described in detail with reference to the attached drawings.

[0035] FIG. 1 is a schematic perspective view of a display device including a flexible cover window according to an embodiment of the present disclosure. FIG. 2 is a perspective view of a display device folded based on a folding axis according to an embodiment of the present disclosure.

[0036] In FIGS. 1 and 2, a foldable display device is illustrated as an example of a display device (100), but is not limited thereto, and the display device (100) may include various types of display devices such as a curved display device, a rollable display device, and a stretchable display device.

[0037] Referring to FIG. 1, a display device (100) may be divided into multiple regions based on a predetermined direction on a display surface (e.g., a top surface). For example, the display surface may have a predetermined width based on a deformation axis (FX; hereinafter 'folding axis') and may be divided into a deformation region (FA; hereinafter 'folding region') that deforms (folds, etc.) along the folding axis (FX) when an external force is applied, and non-deformation regions (NFA1, NFA2; hereinafter 'non-folding region') defined on both sides of the folding region (FA). The display device (100) can output data in various visual forms through the folding region (FA) and the non-folding region (NFA1, NFA2).

[0038] Referring to FIG. 2, the display device (100) can be folded based on a folding axis (FX). FIG. 2 shows a folded form (inner folding) in which the upper surface of the first non-folding area (NFA1) and the upper surface of the second non-folding area (NFA2) face each other, but according to the embodiment, the lower surface of the first non-folding area (NFA1) and the lower surface of the second non-folding area (NFA2) may be folded (outer folding) in which they face each other.

[0039] Meanwhile, the display device (100) may include a cover window that is positioned on top of an internal display panel (LED, etc.) and covers the front of the display panel. If the display device (100) corresponds to a flexible display device, the cover window may also be implemented as a flexible cover window that is deformable in a predetermined area. The flexible cover window may include an optically transparent insulating material. According to an embodiment of the present disclosure, the flexible cover window may include glass. For example, the glass included in the flexible cover window may be implemented as an aluminosilicate-based glass and may correspond to an ultra-thin glass (UTG) having a thickness of about 0.2 mm or less.

[0040] Meanwhile, glass is a material with low ductility, so in order to secure folding characteristics exceeding a certain standard, the thickness of the glass must be reduced. However, if the thickness of the glass is reduced, the strength decreases, so there is a problem in that cracks or breakage occur in the glass even from small external impacts.

[0041] To resolve the aforementioned problem, the present disclosure proposes a structure for improving folding characteristics by reducing only the thickness of the region where deformation occurs (folding region (FA)) of the glass of a flexible cover window, while maintaining the strength of the non-folding region (NFA1, NFA2). Embodiments related thereto will be described below with reference to FIGS. 3 to 8.

[0042] FIGS. 3 to 5 show an example of a cross-sectional view of a flexible cover window cut along A-A' shown in FIG. 1.

[0043] Referring to FIGS. 3 to 5, the flexible cover window (300) may include a glass substrate (310) and a coating layer (330) formed on one side (e.g., the front side) of the glass substrate (310).

[0044] Meanwhile, according to an embodiment of the present disclosure, a recess pattern (320) may be formed in an area of ​​the glass substrate (310) that includes a virtual folding axis (FX). The area including the virtual folding axis (FX) may correspond to the folding area (FA) described above in FIG. 1.

[0045] The recess pattern (320) may have a shape that is recessed to a predetermined depth from one side of the glass substrate (310) (e.g., the top surface in the embodiment of FIG. 3). For example, the recess pattern (320) may form a curved surface with a cross section that is approximately concave and may be formed in a curved direction from the one side toward the other side. The recess pattern (320) may have a shallower overall depth as it moves away from the central region of the display surface of the glass substrate (310), preferably the folding axis (FX), and may have a shape that is approximately symmetrical with respect to the folding axis (FX) or a specific location. This is because a greater deformation force is required when folding as it gets closer to the folding axis (FX).

[0046] Specifically, the recess pattern (320) may be implemented in a form in which a plurality of recesses are partially overlapped and connected. Each of the plurality of recesses may have a curved surface with a cross section that is approximately concave. According to the embodiment of FIG. 3, the plurality of recesses may include a first recess formed in an area including the center of the folding axis (FX) or folding region (FA), second recesses formed on both sides of the first recess, and third recesses formed on one side of the second recesses (the side facing the non-folding region (NFA1, NFA2)). In this case, the distance from the center of the folding axis (FX) or folding region (FA) may increase from the first recess to the third recess.

[0047] Meanwhile, referring to FIGS. 4 and 5, a plurality of recesses may be formed with different widths and depths depending on their distance from the center of the folding axis (FX) or folding area (FA). Specifically, the first recess may be formed to have a first depth (D1) and a first width (W1). Additionally, each of the second recesses formed on both sides of the first recess may have a second depth (D2) smaller than the first depth (D1) and a second width (W2) smaller than the first width (W1). Finally, each of the third recesses formed on one side of the second recess (the side facing the non-folding area (NFA1, NFA2)) may have a third depth (D3) smaller than the second depth (D2) and a third width (W3) smaller than the second width (W2). However, according to the embodiment, the second recess and the third recess may have the same depth and width.

[0048] The flexible cover window (300) may further include a cushioning member (322) that fills the area where the recess pattern (320) is formed. The cushioning member (322) includes a polymer having flexibility or elasticity, thereby enabling smooth deformation of the glass substrate (310) where the recess pattern (320) is formed. According to an embodiment of the present disclosure, the thickness of the cushioning member (322) in the area including the folding axis (FX) is formed to be the thickest, thereby providing sufficient flexibility of the flexible cover window (300) during folding, thereby enabling smooth folding.

[0049] Additionally, the cushioning member (322) can improve the durability of the glass substrate (310) by absorbing at least a portion of the external force applied to the glass substrate (310) or the flexible cover window (300) including the same.

[0050] According to one embodiment, the buffering member (322) may include at least one of an optical clear adhesive (OCA) and a pressure sensitive adhesive (PSA). For example, the buffering member (322) may be formed through a combination of acrylic, epoxy, silicone, urethane, urethane composite, urethane-acrylic composite, hybrid sol-gel, siloxane-based, etc., but is not limited thereto.

[0051] Meanwhile, the buffer member (322) can flatten at least one surface of the glass substrate (310) on which the recess pattern (320) is formed. For example, the buffer member (322) can be filled into the recess pattern (320) so that the thickness of the folding region (FA) and the non-folding region (NFA1, NFA2) of the glass substrate (310) becomes equal. That is, the sum of the thicknesses of the glass substrate (310) and the buffer member (322) can be substantially constant for each region.

[0052] Meanwhile, the buffer member (322) can be implemented so that its refractive index is substantially the same as that of the glass substrate (310). Accordingly, when light is emitted from a light-emitting part (LED, etc.) of a display device equipped with a flexible cover window including the glass substrate (310), the problem of degraded image quality due to abnormal refractive of light in the area where the recess pattern (320) is formed can be prevented.

[0053] As the above-described recess pattern (320) is formed in the folding region (FA), the glass substrate (310) of the folding region (FA) may have a relatively thinner thickness than the glass substrate (310) of the non-folding region (NFA1, NFA2). Accordingly, as the folding characteristics of the folding region (FA) are improved, the decrease in strength of the non-folding region (NFA1, NFA2) can be prevented.

[0054] Meanwhile, the coating layer (330) may be composed of various known materials, such as AF (anti-fouling) film, AR (anti-reflective) film, and scratch-resistant film, in a single layer or multiple layers. The coating layer (330) may be formed according to known methods such as spraying, dipping, and spin coating after a buffering member (322) is filled into the area where the recess pattern (320) is formed.

[0055] FIG. 6 shows another embodiment of a cross-sectional view of a flexible cover window cut along A-A' shown in FIG. 1.

[0056] According to the embodiment illustrated in FIG. 6(a), recess patterns (620a, 620b) may be formed on both sides of a folding region (FA) defined in a glass substrate (610). The shape of each recess pattern (620a, 620b) may be similar to the embodiment of FIG. 3 to FIG. 5, but the maximum depth may be less than half the thickness of the glass substrate (610). According to the present structure, the flexible cover window (600) can be folded more smoothly in both directions (inner folding and outer folding).

[0057] The buffer member (622a, 622b) filled in the area where the recess pattern (620a, 620b) is formed, and the coating layer (630) formed on one side of the glass substrate (610) may be the same as the buffer member (322) and coating layer (330) described above in FIGS. 3 to 5.

[0058] According to the embodiment illustrated in FIG. 6(b), the sum of the maximum depths of the recess patterns (720a, 720b) ​​formed on both sides of the folding area (FA) can be formed to be greater than the thickness of the glass substrate (710). In this case, the recess patterns (720a, 720b) ​​can be connected to each other, and glass may not be present in the area where the recess patterns (720a, 720b) ​​are connected. According to the structure, the flexible cover window (700) may be implemented as a stretchable cover window that is not only folded in both directions but also stretched / contracted by a predetermined length in the AA' direction.

[0059] The buffer member (722a, 722b) filled in the area where the recess pattern (720a, 720b) ​​is formed, and the coating layer (730) formed on one side of the glass substrate (710) may be the same as the buffer member (322) and coating layer (330) described above in FIGS. 3 to 5.

[0060] FIGS. 7 to 8 show an example of a manufacturing process for a flexible cover window according to the embodiments of FIGS. 3 to 5.

[0061] Referring to FIG. 7, a protective coating layer (810) may be formed on at least one surface of a glass substrate (800). For example, the protective coating layer (810) may be formed by an inkjet printing technique, but is not limited thereto, and the protective coating layer (810) may also be formed by a photolithography technique, etc.

[0062] When an inkjet printing technique is used, a protective coating layer (810) can be formed by selectively depositing a coating liquid on at least one surface of a glass substrate (800) through one or more inkjet heads, and by curing the deposited coating liquid by heat or UV light.

[0063] The fact that the coating solution is selectively deposited on one side of the glass substrate (800) may mean that the coating solution is not formed over the entire area of ​​one side of the glass substrate (800) but may be formed only in a part of the area. In this case, the area where the coating solution is not formed may correspond to an exposed area where one side of the glass substrate (800) is exposed to the outside.

[0064] Since the portion of the glass substrate (800) corresponding to the exposed area is not protected by the protective coating layer (810), it can be etched to a predetermined depth by depositing an etching solution on one side of the glass substrate (800) during a subsequent chemical polishing step. For example, the exposed area may include the folding area (FA) described above, and the thickness of the folding area (FA) may be thinner than the thickness of the area where the protective coating layer (810) is formed according to the chemical polishing step.

[0065] After the protective coating layer (810) is formed, the glass substrate (800) can be cut into cells of a predefined size. The glass substrate (800) can be cut according to known methods or means, such as a laser beam or a diamond wheel.

[0066] To describe the case where a glass substrate (800) is cut by a laser beam, a cutting line for cell-unit cutting is defined on the glass substrate (800), and a laser beam can be irradiated along the area corresponding to the cutting line. The laser beam used for cell-unit cutting of the glass substrate (800) may be an ultrashort pulse Bessel beam. The long, uniform beam spot of the zero-order Bessel beam, which is free of diffraction, can have an advantage in creating long internal structural deformations that penetrate the glass substrate (800), and can enable stealth dicing or control over the propagation of cracks formed inside the glass substrate (800). The stealth dicing is a process that weakens brittle materials by causing changes in the internal structure prior to breaking the glass substrate (800) using an auxiliary device, etc. According to an embodiment of the present disclosure, by cutting a glass substrate (800) using a stealth dicing process with a Bessel beam in the laser cutting step, advantages such as high-speed cutting, reduced chipping, and no generation of chemicals may be provided. However, even if the glass substrate (800) is cut using a stealth dicing process, non-uniform conditions such as chipping may exist on the cut surface of the glass substrate (800') cut in cell units.

[0067] Meanwhile, a protective coating layer (810) may not be formed in the area corresponding to the cutting line. However, depending on the embodiment, a protective coating layer (810) may be formed in the area corresponding to the cutting line.

[0068] According to an embodiment, the laser beam may be irradiated at a predetermined location of the exposed area described above before the chemical polishing step is performed to deform the internal structure of the exposed area, thereby improving the etching speed and precision in the chemical polishing step.

[0069] Referring to FIG. 8, a recess pattern (830) can be formed through a chemical polishing (etching) process on a glass substrate (800'). For example, the chemical polishing process can be performed by depositing an etching solution over the entire surface of the glass substrate (800') and maintaining contact between the glass substrate (800') and the etching solution for a predetermined period of time.

[0070] According to the embodiments, an acid etching method may be utilized in the chemical polishing process. Acid etching can typically be performed by controlled chemical attack using an aqueous solution based on hydrofluoric acid. Acid etching may be performed one or more times. Generally, the pH of the acidic aqueous solution used for this purpose is 0 to 5, and in addition to the hydrofluoric acid itself, it may contain salts of this acid, other acids, e.g., HCl, H2SO4, HNO3, acetic acid, phosphoric acid and / or salts thereof (e.g., Na2SO4, K2SO4, (NH4)2SO4, BaSO4, etc.), and small amounts of other adjuvants. For example, alkali metal and ammonium salts such as sodium difluoride, potassium difluoride, and ammonium difluoride are generally preferred. The acid etching step according to the present invention may advantageously be performed by controlled acid attack for a time (e.g., more than 2 minutes) that may vary depending on the acid solution used and the desired result.

[0071] By the above etching solution, an exposed area on the surface of the glass substrate (800'') where a protective coating layer (810) is not formed can be etched to a predetermined depth in response to the reaction with the etching solution. For example, the exposed area can be anisotropically etched in response to the reaction with the etching solution, thereby forming a plurality of recesses (822, 824a, 824b, 826a, 826b) having a concave cross-section of the etched surface. And as the anisotropic etching is performed for a predetermined time, a plurality of recesses (832, 834a, 834b, 836a, 836b) whose size has increased can overlap with a part of an adjacent recess to form an integrally connected recess pattern (830). In this process, part of the recess may extend to the lower part of the area where the protective coating layer (810) is formed, and as a result, part of the protective coating layer (810') may be removed from the glass substrate (800''').

[0072] Meanwhile, the width and depth of the plurality of recesses (832, 834a, 834b, 836a, 836b) may be related to the width of the exposed area. As illustrated in FIGS. 4, 5 and 8, it can be seen that the width of the first exposed area corresponding to the first recess (832) having the largest width (W1) and depth (D1) is greater than the width of the second exposed area corresponding to the second recess (834a, 834b) having a width (W2) and depth (D2) smaller than the first recess (832). Similarly, it can be seen that the width of the third exposed area corresponding to the third recess (836a, 836b) having a width (W3) and depth (D3) smaller than the second recess (834a, 834b) is smaller than the width of the second exposed area.

[0073] According to an embodiment, the chemical polishing process may be performed with multiple etching steps having different etching conditions. For example, the chemical polishing process may consist of a first etching step of depositing an etching solution of high concentration or low pH for rapid formation of a recess pattern (830), and a second etching step of depositing an etching solution of relatively low concentration or high pH for uniform etching surface of the formed recess pattern (830).

[0074] Meanwhile, chemical polishing (healing) of the cut surface of the glass substrate (800') is performed by the above etching solution, so that chipping and other defects present on the cut surface can be removed and the cut surface can be polished more smoothly.

[0075] After the recess pattern (830) is formed, the protective coating layer (810') remaining on the glass substrate (800''') can be removed (peeled off). For example, the protective coating layer (810') can be removed by dipping the glass substrate (800''') into a cleaning solution or by spraying the cleaning solution onto the protective coating layer (810'). The cleaning solution may include an aqueous solution or an organic solution containing a detergent or an organic solvent, and the temperature of the cleaning solution may be higher than the ambient temperature. According to an embodiment, the etching solution remaining on the glass substrate (800''') can also be removed by the cleaning solution.

[0076] After the protective coating layer (810') is removed, a buffer member (840) may be filled into the area where the recess pattern (830) of the glass substrate (800''') is formed. Although not illustrated, after the buffer member (840) is filled, a coating layer (330 in FIG. 3') may be formed on the glass substrate (800''').

[0077] FIG. 9 is a cross-sectional view of a flexible cover window according to one embodiment of the present disclosure.

[0078] Referring to FIG. 9, a plurality of recesses (911, 912, 913, 914) may be formed in the glass substrate (910) of the flexible cover window (900) in a manner similar to that described in FIG. 3 to 8. At this time, the plurality of recesses (911, 912, 913, 914) may be formed on the bottom side of the glass substrate (910), but are not limited thereto. FIG. 9 illustrates an embodiment in which four recesses are formed, but the number of recesses is not limited thereto and can be varied. According to the embodiment, the size of the recesses (911, 912, 913, 914) may be smaller closer to the folding axis (FX; see FIG. 1), but is not necessarily so.

[0079] A buffer member (922, 924, 926, 928) may be filled in the area where a plurality of recesses (911, 912, 913, 914) are formed. The buffer member (922, 924, 926, 928) may be made of the same material as the buffer member (322) of FIG. 3. A coating layer (930) may be formed on the upper surface of the glass substrate (910), and the coating layer (930) may correspond to a configuration substantially identical to the coating layer (330) described above in FIG. 3.

[0080] Meanwhile, unlike the embodiments of FIGS. 3 to 8, the thickness of the glass substrate (910) in the portion corresponding to each recess (911, 912, 913, 914) may be formed in a shape that generally becomes thinner as it moves from the center of the folding area to the left or right. For example, the first thickness (T1) of the glass substrate (910) may be formed to be about 40 to 500 micrometers, and the second thickness (T2), which is the minimum thickness of the glass substrate (910) in the area corresponding to the recess (911, 912), may have a value greater than or equal to the third thickness (T3) and less than the first thickness (T1). Furthermore, the third thickness (T3), which is the minimum thickness of the glass substrate (910) in the area corresponding to the recess (913, 914), may have a value smaller than the first thickness (T1) and may be formed to be, for example, about 20 to 70 micrometers.

[0081] Meanwhile, a reinforcing section (915, 916, 917) may be defined between each recess (911, 912, 913, 914). The reinforcing section (915, 916, 917) may correspond to an area where the glass substrate (910) is etched relatively less between each recess (911, 912, 913, 914) and is thicker than the glass substrate thickness of the adjacent recess portion. Each of the reinforcing sections (915, 916, 917) has a thickness (T4, T5) greater than the glass substrate thickness (T2, T3) of the area corresponding to the adjacent recess (911, 912, 913, 914), thereby improving structural stability when the glass substrate (910) is deformed. According to the embodiment, the thickness (T4, T5) of the glass substrate (910) in the area corresponding to each of the reinforcing portions (915, 916, 917) may have a larger value as it approaches the folding axis (FX; see FIG. 1). In this case, the thickness (T4) of the first reinforcing portion (915) may be greater than the thickness (T5) of the second reinforcing portion (916) and the third reinforcing portion (917).

[0082] FIG. 10 is a cross-sectional view of a flexible cover window according to one embodiment of the present disclosure.

[0083] Referring to FIG. 10, a plurality of recesses (1012a, 1012b) spaced apart from each other may be formed on each side of the folding area of ​​the glass substrate (1000) in the flexible cover window (1000). Each of the plurality of recesses (1012a, 1012b) may have the same shape and size, but is not limited thereto, and the width or depth of the recesses may vary depending on the distance from the folding axis (FX).

[0084] Meanwhile, when viewed from the AA' cross-section, the position of the upper surface recess (1012a) formed on the upper surface and the position of the lower surface recess (1012b) formed on the lower surface may differ from each other. For example, the lower surface recess (1012b) may not be formed at the location where the upper surface recess (1012a) is formed, and the upper surface recess (1012a) may not be formed in the area where the lower surface recess (1012b) is formed. In this case, the glass substrate (1010) of the folding area may be implemented in a zigzag shape. By forming recesses on both sides of the glass substrate (1010) and the glass substrate (1010) having a zigzag shape, the flexible cover window (1000) may be implemented as a double-sided foldable cover window or a stretchable cover window.

[0085] If the distance between the maximum depth points of each adjacent recess is defined as the pitch (P), the pitch (P) can be formed to be larger than the maximum width of the recess, and according to the embodiment, it can be more than twice the maximum width of the recess. In addition, the depth (T7, T8) of each recess (1012a, 1012b) can be less than half the thickness (T6) of the glass substrate (T6). For example, the thickness (T6) of the glass substrate can be formed in the range of 100 to 1000 micrometers, and in this case, the depth (T7, T8) of each recess can be formed in the range of 25 to 500 micrometers. Accordingly, the reduction in thickness of the glass substrate (1010) due to the upper surface recess (1012a) and the lower surface recess (1012b) being excessively close is minimized, so that a minimum thickness for stability during deformation of the glass substrate (1010) can be ensured.

[0086] The description of the above-described embodiments is merely an example provided with reference to the drawings for a more thorough understanding of the present disclosure, and should not be interpreted as limiting the technical scope of the present disclosure.

[0087] Furthermore, it will be apparent to those skilled in the art to which this disclosure pertains that various changes and modifications are possible within the scope of the basic principles of this disclosure.

Claims

Claim 1 A glass substrate comprising a deformation region that deforms along a deformation axis extended in one direction upon application of an external force, and a non-deformation region connected to the deformation region, and a recess pattern formed in the deformation region, wherein the recess pattern comprises a plurality of recesses etched to a predetermined depth from one surface of the glass substrate, and wherein the plurality of recesses each comprise a first recess formed at a position symmetrical with respect to the deformation axis; A flexible cover window comprising a first recess and a second recess formed at a position symmetrical with respect to the deformation axis, which is spaced relatively apart from the deformation axis compared to the first recess, wherein the glass substrate further comprises a plurality of reinforcing members formed between adjacent recesses among the plurality of recesses, wherein the thickness of the first reinforcing member formed between the first recesses among the plurality of reinforcing members is thicker than the thickness of the second reinforcing member formed between the first recess and the second recess, the width of the first recess is formed narrower than the width of the second recess, and the thickness of the glass substrate in the area corresponding to the first recess is formed thicker than the thickness of the glass substrate in the area corresponding to the second recess. Claim 2 A flexible cover window according to claim 1, wherein the thickness of the first reinforcing part is thicker than the thickness of the glass substrate in the area corresponding to the first recess. Claim 3 A flexible cover window according to claim 1, wherein the thickness of the first reinforcing part is formed to be the same as the thickness of the glass substrate in the area where no recess is formed. Claim 4 In claim 1, the first reinforcing member is formed at a position overlapping with the deformation axis, forming a flexible cover window. Claim 5 A flexible cover window according to claim 1, wherein the plurality of recesses further include a third recess formed on the opposite side of the first recess among the two sides of each of the second recesses, and the thickness of the third reinforcing part formed between the second recess and the third recess is thinner than the thickness of the first reinforcing part. Claim 6 A flexible cover window according to claim 1, further comprising a cushioning member filled in an area corresponding to the plurality of recesses, wherein the cushioning member comprises at least one of OCA (optical clear adhesive) and PSA (pressure sensitive adhesive). Claim 7 A flexible cover window according to claim 6, wherein the sum of the thicknesses of the glass substrate in the area filled with the buffer member and the buffer member is the same as the thickness of the glass substrate in the area not filled with the buffer member. Claim 8 A flexible cover window according to claim 1, further comprising a coating layer formed on at least one surface of the glass substrate, wherein the coating layer comprises at least one of an AF (anti-fouling) film, an AR (anti-reflective) film, and a scratch-resistant film. Claim 9 delete Claim 10 delete Claim 11 A display device comprising a flexible cover window as described in any one of claims 1 to 8.

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